The image was stark and simple. In a split second, it shocked the pupils out of that sense of invulnerability which is so often an enemy to young people.
What they saw was a mobile phone, not unlike their own, but this one was presented as a cemetery headstone bearing the message "RIP 4U".
"It was profound," says Patty Owen, a personal health and social education specialist at Dalziel High in Motherwell. "It spoke their language, reflected their culture and delivered a message about the risks of the real world.
"They were shocked, more than they would have been by pictures of road accidents."
That shock may have saved some of their lives. Two 14-to 18-year-olds are killed every day in road accidents. To a generation immersed in sophisticated imagery that allows people to drive computer animated cars at 200mph, the world appears less risky than in reality.
However, as drivers, passengers or pedestrians, they are an at-risk group in Crash Magnets, a DVD developed by Road Safety Scotland as part of a classroom road safety campaign also named Crash Magnets. Launched by Tavish Scott, the Transport Minister, after a pilot study in 20 schools, including Dalziel High, the DVD and accompanying game cards will become part of the senior curriculum.
The 10-lesson resource covers driver distraction, speed, the cruise culture and drink and drug driving. It explores accidents, emergency services and includes role playing.
Driving develops independence and defines teenagers as adults, but it also carries risks.
"We've had a vehicle safety course," says Ms Owen. "Our school has a high proportion of pupils who have access to cars.
"But this generation is like no other, surrounded by imagery which, by its sophistication, accords special status to the trivial. What Crash Magnets has done is apply that sophistication to a subject that is anything but trivial. It is mimicking computer game technology in a manner that makes risks real and relevant.
"The graphics are impressive. I can't forget the mobile phone headstone. It provoked huge feedback because it was relevant.
"In the past, shock value was accrued by pictures of crashes. How can that work today when you can shoot hundreds of people in your living room? Or race a car? Or see any number of shocking images? It desensitises.
"Because young people are using technology in a decision-making manner, we must deliver messages by the same means, allowing them to see the images, evaluate them and make choices.
"That is the strength of this resource. Evaluation by the pupils made it stimulating and memorable. I believe it could already have made the difference between a person dying through lack of thought or surviving because they now have powerful images in their minds about how to behave."
At Dalziel High, the Crash Magnet course will be integrated into other aspects of PSE.
"We'll dedicate special periods to it for several weeks, then evaluate what the best format is for going forward," says Ms Owen.
"We must remember that this is not just about boy racers. Modern girl is as likely to be driving."
Ms Owen believes it is important to involve local authority road safety officers in lessons.
"To make the course more meaningful, you have to talk about the actual streets young people will drive on. The involvement of local road safety officers will give it a sense of place."
She also believes the course should evolve. "To maximise its power, it must be constantly relevant. Technology is changing; the resource must keep pace."
Kate Wheaton, the education adviser to Road Safety Scotland, agrees. She says: "We have that factored in. It must remain recognisable. I'm already looking at hairstyles in the DVD."
Ms Wheaton hopes teachers will have the programme running by June. "I hope young people have it deep in their psyche before the holidays."